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The unwanted flow of water in the reverse direction, posing a risk to potable water supplies.
What is backflow?
The category of wholesome drinking water.
What is fluid category 1
An air gap suitable for all fluid categories
What is an AA air gap
A device used to protect against fluid category 3 hazards
What is a double check valve
The regulations listing the five fluid categories of water
What is The Water Supply (Water Fittings) Regulations 1999
Water with a slight hazard, such as heated water in a home.
What is fluid category 3
The reverse flow caused by higher downstream pressure.
What is backpressure
The type of air gap used in a dental surgery for high-risk fluid category 5
What is an AB air gap
The most hazardous water category.
What is fluid category 5
A verifiable mechanical backflow prevention device for fluid category 4
What is an RPZ valve
A non-mechanical backflow prevention device for commercial washing machines.
What is an AD air gap
A device used in sealed heating systems to connect with the cold water supply.
What is a CA backflow preventer
The result of improper protection at a cross-connection
What is cross-contamination
To prevent the mixing of fluid categories in a bath/shower mixer
What is a HC diverter
The fluid category associated with industrial processes
What is fluid category 4
A tap requiring a minimum spacing of 20mm from the outlet to the spillover level.
What is a G ½ basin tap
To admit air and break siphonic action during back siphonage
What is the function of a DC pipe interrupter
A situation requiring whole site protection
What is a high-risk industrial process
300mm in some configurations
What is the minimum air gap for fluid category 5
A device for backflow protection in hot or cold systems up to 90°C.
What is an EB non-verifiable single check valve
To protect cistern water from dust, vermin, and fluid category 5
What is the role of an AB air gap with a weir overflow
A strategy to prevent contamination of the mains supply at high-risk installations
What is whole site protection
An air gap used in cisterns open to the atmosphere for fluid category 3
What is a type AG air gap
Why must backflow preventers be installed indoors
To avoid damage from freezing
The primary cause of back siphonage
What is a vacuum effect in water mains